Motor-driven leveling support



S. G. IS SERSTEDT MOTOR DRIVEN LEVELING SUPPORT Filed Sept. 25, 1942 mvmron swam/0 G. 1555/7572'07' Patented Dec. 6, 1949 UNITED STATES PATENT OFFICE MOTOR-DRIVEN LEVELING SUPPORT ration of Delaware Application September 23, 1942, Serial No. 459,439

4 Claims. 1

The present invention is directed to a leveling support for cameras and other devices which are carried by such vehicles as airplanes which are subject to various inclinations from a normal or horizontal position.

An object of the invention is to provide an antomatic leveling device adapted to be mounted on an object subject to inclinations from 2. normal position.

Another object of the invention is to provide an aerial camera mount which will automatically maintain a camera in level position even though the airplane itself is subject to rolling and pitchin movements.

Another object is to provide such a levelling support in which the camera or other device may be positioned about a vertical axis in order to align the device with the actual direction of flight and to compensate for drift.

It is also an object of the invention to provide a remote control for the adjustment of the device about a vertical axis, together with a remote indicator for such adjustment.

A further object of the invention is to provide a motorized aerial C-A-M-E-R-A leveling device in which the C-A-M-E-R-A is supported in a gimbal which is in turn arranged to rotate about a vertical axis with respect to the airplane.

Another object is to provide a leveling device equipped with motor means and gravity responsive motor control means, the motor control means being adapted to deenergize the motor means when the angle of tilt is beyond a predetermined degree.

Another object is to provide a leveling device rotatable about a vertical axis in which the various motors are so disposed as to be substantially in balance.

Further objects and advantages of my invention will be apparent from the following detailed description, claims, and drawing, in which Figure l is a plan view of an automatic aerial camera leveling device embodying my invention,

Figure 2 is a schematic wiring diagram of the control apparatus associated with the device of Figure 1,

Figure 3 shows the gravity responsive motor control means in more detail than it is shown in Figure 2, and

Figure 4 shows a modification of the gravity responsive motor control means of Figure 3.

Aerial cameras, especially those used in aerial survey work, are commonly mounted in a support which permits universal movement of the camera through a limited range. This arrangement enables the camera operator to keep the camera approximately level through manual manipulation even though the airplane rolls and pitches due to uneven air conditions. As indicated above, the present invention provides a way to automatically maintain an aerial camera in level position during flight. Not only does this arrangement relieve an operator from this task but it also provides more accurate control than may be had manually.

It is also common practice to provide means for adjusting the camera about a vertical axis in order that the camera may be lined up with the actual direction of flight even though a cross wind is causing the airplane to drift. The invention includes means for adjustin the camera in azimuth about this vertical axis from a remote point such as the pilots station.

A camera leveling device incorporating the various features of my invention is shown in Figure 1 of the drawing. The electrical connections have been omitted from Figure 1 since it is felt that incorporating them therein would confuse rather than clarify the disclosure. Consequently they are illustrated diagrammatically in Figure 2.

Referring now to Figure 1, a supporting ring l0, which is adapted to be carried in a normally horizontal position in the interior of an airplane, and above an opening in the bottom thereof, has a V-shaped annular groove l I in its upper surface. An octagonal frame I2 is provided with four rollers M which are so shaped as to engage the V-shaped groove H in the ring [0. The frame I2 is supported by the ring Ill through the rollers l4 so as to be rotatable about a normally vertical axis with respect to the airplane which is carrying the apparatus.

It is common to refer to the adjustment of the frame l2 about a vertical axis as the azimut adjustment. The ring It has a portion of its interior surface formed in the shape of gear teeth It, which are adapted to cooperate with a pinion l1, pivotally supported by an extension 18 of the frame l2 so as to rotate about a vertical axis. An electric motor l9 carried by the frame [2 is adapted to turn the pinion I! through a worm 20. The motor [9 is reversible and will be described more fully in connection with the wiring diagram of Figure 2. An electrical follow-up device 22 is also positioned by the motor IS. The follow-up device 22 and its operation will also be described more fully in connection with Figure 2.

A gimbal ring 25 is pivoted in the frame l2 on trunnions 26 and 21, so that the gimbal ring may rotate about a normally horizontal axis. A reversible electric motor 38 carried by the frame I2, cooperates through a worm 3| with a gear 32 which is fixed on the trunnion 26. For the Durpose of simplicity in illustration, the motors l9 and 38 have been shown to be relatively small. Actually the motors l9 and 38 must be capable of considerable power and therefore are fairly heavy. The motor 38, for instance, must be capable of adjusting the gimbal ring 25 with respect to the frame I2 rapidly enough to compensate for movements of the airplane in fairly rough air. It should be noted that the motors l9 and 38 have been mounted on the frame l2 at points diametrically opposed with respect to the vertical axis. Thus, the motors I9 and 38 impose no eccentric load which would tend to load the motor I9 unevenly for different positions of the frame l2 when the ring I8 is tilted from its normally horizontal position. a

A camera supporting member 34 is pivoted in the gimbal ring 25 on the trunnions 35 and 36, so that the member- 34 may rotate about a normally horizontal axis. A reversible electric motor 38 drives a worm 39 to position a gear 48 which is fixed ,to the trunnion 35. The electric motor 38 is supported by the gimbal rin 25 at one side of the axis of the gimbal ring extendin through trunnions 26 and 21, and a counter-weight 42 is mounted on the opposite side of the gimbal ring to counterbalance the motor 38. It should be noted that th weight 42 is so positioned that it counter-balances motor 38 not only about the horizontal axis extending through trunnions 26 and 21, but also about the vertical axis of the device. An aerial camera 45 is carried by the' camera supporting member 34. The gimbal ring 25 together with the camera supporting member 34 constitutes a gimbal which carries the camera 45 in the airplane.

The reversible electric motor 38 is controlled by a first gravity responsive switching means 46, which is carried by the gimbal ring 25 and by a second gravity responsive switching means 41, which is carried by the frame I2. The switching means 46 and 41 will be more fully described in connection with Figures 2, 3 and 4. The reversible electric motor 38 likewise is controlled by a first gravity responsive switching means 49, fixed with respect to the camera supporting member 34, and also by a second gravity responsive switching means 58, carried by the frame l2. The switching means 49 and 58 will also be described in connection with Figures 2, 3 and 4.

By tilting of the gimbal ring 25 on its trunnions 26 and 21, and by tilting of the supporting member 34 on trunnions 35 and 36', the camera 45 may be maintained in level position, regardless of inclinations of the ring l8.

The reversible electric motors I9, 38 and 38 of Figure 1 are automaticall controlled and the automatic control circuits therefor are shown in Figure 2. Alternating current for operating the various reversible motors is supplied by a transformer 52, which includes a primary winding 53 and a low voltage secondary winding 54.

The angular position of the frame 12 with respect to the ring l8, and therefore with respect to the airplane, is controlled remotely by means of a manually adjustable knob 56. The knob 58 positions a slider 68 and a pointer 51, which cooperates with a stationary scale 58. The scale 58 may be suitably calibrated, and ring 18 may I be properly oriented when it is being installed in the craft, so that pointer 51 cooperates with scale 56 to indicate the angular position of the camera mount with respect to a line passing through the nose and tail of the aircraft. If the operator sets the knob 56 so that the angle indicated on scale 58 corresponds to the angle of drift of the aircraft, then the camera is positioned, by the mechanism described below, so as to be aligned in azimuth, with the line of flight of the aircraft.

Slider 68 is actuated by knob 56 and cooperates with an electrical resistance 6|. The position of the slider 68 on the resistance 61 determines the deenergized position of the motor l9 and hence the position of the frame l2 with respect to the ring 18.

A balanced relay 63 has an armature 64 carrying a contact blade 65, the armature 64 bein pivoted at 61. The position of the armature 64 and hence of the contact blade 65 is determined by the relative energization of relay coils 68 and 69. The relay 63 also includes a pair of stationary contacts 12 and 13, the contact blade 65 engaging the contact 12 when the coil 68 is more highly energized than coil 69, and engaging the contact 73 when the coil 69 is more highly energized than the coil 68. When the energization of the coils 69 and 18 is substantially equal the contact blade 65 takes a mid-position as illustrated.

The motor I9 is of the split-phase induction type and includes an armature I5 and two windings 16 and TI. The motor l9 also includes a condenser 19 through which one or the other of the windings 16 or 11 is energized. The current flowing through the winding which is energized through the condenser 19 leads the current through the other coil in time phase by substantially electricaLdegrees. The direction of rotation of the armature I5 depends on which of the two windings is energized through the condenser 19. Alternating electric current is supplied to the motor l9 from the upper terminal of the secondary 54 of the transformer 52, through conductors 8|, 82, and 83, and the switch blade 65 of the relay 63. When the winding 68 of the relay 63 is more highly energized, the contact blade 65 engages the contact 12 and current flows through the contact 12, wire 84, the winding 16 and conductors 81, 88, and 98 back to the lower terminal of secondary 54. Current also flows through the condenser 19 and the winding 11 in series. The current in the winding 11 therefore leads the current in the winding 16 by substantially ninety electrical degrees and the armature rotates, for example, in a clockwise direction. When the coil 69 of the relay 63 is more highly energized than the coil 68, the switch blade 85 engages the stationary contact I3, and the motor I9 is energized through the wire 85 so that current flows directly through the winding 11 and flows through the winding 16 by way of the condenser 19.

The current flowing through the winding 18 now leads the current flowing through the winding 11 by substantially ninety degrees and the armature 15 rotates in the opposite, or, to carry on the example, counter-clockwise direction.

The follow-up device 22 referred to in connection with Figure 1 includes a reduction gear box 93, which mechanically interconnects the armature 15 of the motor I9 and a slider which engages an electrical resistance 96, in a circuit including the coils of the balanced relay 63 and the resistance 6|. The relay coil 68 is energized from the secondary 5401 the transformer 52 through the conductor 8|, slider 68, the portion of the re-- ondary 50.

5 sistance 6| to the left of the slider 60, a conductor 90, the relay coil .68, a conductor 99,-theportion of the resistance 96 to the left of the slider 95, and conductors I and 90 back to the secondary 54. The relay winding 69 is energized from the secondary 54 of the transformer through theconductor SI, slider 60, the portion of the resistance 6| to the right of the slider60, conductor I02, the relay coil 69, wire I03, the portion of the resistance 96 to the right of the .slider 95, the

comprises two mercurytype switches Ill and I06. which are tilted slightly in oppositediev rections so that-when the gimbal ring.-2l', on which they are moun e is in its neutral position, the circuits through both of these switches I are open. The angle of tilt from normal posislider 95, and conductors I00 and 90 to the sec-.

When the total resistance in series of the relay coils 60 and 69 is the same, the. current flowing in each coil is the same and the armature 54 and contact blade 65 are in mid-position. If the slider 60 is moved to the left with respect to the resistance 6i, the resistance in series with the coil 68 is reduced and the current through it is increased. At the same time, the resistance in series withcoil 09 is increased-and the current through it is thereby decreased. Hence the coil 68 is more highly energized than the coil 69 and the contact blade is moved into engagement with the contact 12 to run the armature I5 of the motor I9 in a direction such that the follow-up slider 95 is moved toward the right with respect to the resistance 96 to increase the resistance in series with the relay coil 69 and decrease the resistance in series with coil 69. When the resistance in series with the coil 60 is again equal to the resistance in series with the coil- 69, the contact blade 65 againmoves to its mid-position and the motor I 9 is deenergized.

Likewise, when the slider 60 is moved to-the right with respect to the resistance 6I the resistance in series with the coil 69 is decreased.

with each' and the resistance in series with the coil is increased. The coil 69 is therefore more highly energized, and moves the armature 64 to cause" engagement of blade 65 with the contact 13. The motor I9 is therefore energized to rotate in a direction such as to move the slider 95 toward the left with respect to the resistance 96 so as to increase the resistance in series with the windin 69 and decrease the resistance in series with winding so. When the slider 95 has moved to the left sufliciently so that the total resistance'in series with each of the relay coils 66 and 691s again equal, the contact blade 65 again returns to midposition and the motor is deenergized. Thus it will be seen that for every position of the slider 60 and of the pointer 51 which cooperates with the indicia 58, there is a definite position for slider 95 and for the frame I2, both of which are driven I simultaneously by the motor I9. Hence, by properly setting the knob 56, pointer 51 and the slider 60 to compensate for the drift of the airplane, the motor I9 turns the pinion I! to position the frame I2 and therefore the camera 45 with respect to tion necessary for these switches, to. close their Likewise when the motor is energized through the mercury switch I06, current passes-directly through the winding I09 and through the winding I06.-by way of the condenser III. The respective modes of energizationof the motor 00 result in rotation'of the armature I01. in op posite directions. It will be understood. that these directions of rotation are such that the :armature. I01, which drives the gear 32 through.

the worm 3I, will tend to restore the gimb ring to its neutral position.

The circuit'through which the motor is,

energized also includes the gravity responsive switching means 41 which is mounted on the frame I2. The switching means 41 is illustrated in Figures 2 and 3. It includes a pair of normally closed mercury switches H2 and II 3. The, energizing circuit i'ormotor 90 passes through both of theseswitches in series. These switches are inclined .at a somewhat greater angle with respect to the horizontal than are the switches 1 I06 and I00, and serve the purpose of stopping operation of the motor when the inclination of the airplane exceeds a predetermined. angle. A

suitable angle of-tilt Iorthese switches may be 20. Hence when 'theairplane is tilted at an angle greater than 20 with respect to horizontal,

themotor 001s deenergized and makes'no attempt to maintain the camera in its level posithe ring I0, so that the camera 45 is in line with I the true direction of flight.

As mentioned connection with Figure l, the motors 30 and 38 are controlled by gravity responsive switching means. The reversible electric motor 30 which controls the angular relationship between the gimbal ring 25 and the frame I0 is controlled primarily by the gravityresponsive switching means 46.

It is desired to maintain the gimbal ring 25 in a neutral position such that the axis through the trunnions and 36, on which the camera is mounted is horizontal. As seen in Figure 2 and more clearly in Figure 3, the switching means tion. This feature is desirable since it is never desired to take pictures'when the airplane is tilted at a greater angle than 20, and also 'because the various motors and switches are interconnected'by flexible lead wires which permit only limited relative movements of the various parts. Also the camera may be of such a construction that its movements in the gimbal ring 25 and is the frame I2 mustbe limited in order to prevent injury'of the parts. Since the mercury switches I I2 and I It are connected inseries, tilting of the airplane su flflciently in either di-' rection will result in deenergization oi the motor.

The motor 20 is energized from the secondary 54 of the transformer 52 through conductors 0|,

02, II5,' mercury switch II2, mercury switch III,

a conductor I I6, and one or the other of the mercury switches I05 and I00. If the gimbal ring 25 becomes tilted in such a direction that. the mercury switch I05 is making contact, the winding I00 is energized directly and the winding I09 is energized through the condenser H0, and the armature I 01 rotates in one direction. The remainder of the circuit may be traced through.

conductors H0, H9, 90, and to' the secondary direction, the circuit is completed through the mercury switch I and the winding Ill is energized directly while the winding III is energized through the condenser I II and the armature II'I rotates in the opposite direction.

The motor 28,. which positions the camera supporting member 24 and the camera 4! with respect to the gimbalring 25, is controlled by gravity responsive switching means 49 and it, as mentioned in connection with Figure I. The

4 switching means 42 corresponds to the switching means It whichcontrols the motor 20, and the switching means 50 corresponds to the switching means .41. The operation of the switching means-li and Ii. is also exactly the same as the operation of the-switching means 48 and 41 except that they are mounted at right angles to the switching means 46 and I1, and hence respond to pitching oi the plane about a lateral axis rather than to rolling" of the plane about a longitudinal axis. Therefore it is not believed that it is necessary to describe either the circuits or their operation in detail. Any inclination of the camera 45 and hence of the switching means 49 from a horizontal position with respect to the axis passing through trunnions 35 and 2 results in operation of the motor 38 to correct this condition. Likewise, should the airplane nose up or down to a sufficient degree, the switching means it deenergizes the motor 38 so that it makes no further attempt to maintain the camera in level position.

An alternative form of gravity responsive switching means is shown in'Figure 4. This device, which is generally indicated at I20, may be substituted for either of the gravity responsive switching means 46 and 49. The same limit switch means 41, previously described, is used in this modification and includes the two normally closed mercury switches H2 and H3 which open the circuit in case the airplane is tilted an excessive amount.

The switching means I includes a pair of oppositely inclined mercury switches I2I and I22, which are adapted to energize the motor when the camera is tilted a predetermined angle in either direction from its normal position. These switches may require a tilt of from normal position in order to cause energization of the motor. A second pair of mercury switches I24 and I25 are so mounted that when the camera is tilted in a predetermined relatively small angle in either direction from its normal or level position, the motor windings will be energized through resistances I26 and I2'I, respectively. The switches I24 and I25 may be so mounted that an angle of tilt of V in either direction from level position, results in energization of the motor. When the motor windings are energized through the resistances I26 or' I2I, the motor armature turns at a slower speed than when energized directly, as is the case when they are energized through the switches I2I or I 22. This arrangement provides a somewhat more accurate control of the leveling of the camera than is provided with the arrangement previously described. On slight inclinations of the camera, the motors are operated at slow speed to correct the condition while when a larger inclination occurs, the motors correct this larger error somewhat more rapidly.

From the foregoing description, it will be apparent that I have provided a leveling support particularly adapted for use with aerial cameras which is automatic in itsoperation, and therefore requires no attention from an operator. The automatic positioning of the camera is also much more accurate than is possible when an operator manually attempts to maintain the camera level. An azimuth control by means of which the drift of the airplane may be compensated for, has been provided, which may be remotely adjusted by the airplane pilot who has other instruments at his command to indicate the proper setting of this control.

While I have shown and described my invention as applied to a support for aerial cameras on aircraft, it will be readily recognized that the same principles may be applied to the support of other devices, and that my invention is not limited to use on aircraft.

Various features of this invention may be embodied in apparatus of difierent form andit is o be understood therefore, that I am to be iimited only by the scope of the appended claims.

I claim as my invention:

1. In a leveling device, in combination, supporting means, a first member carried by said supporting means for rotation about a normally vertical axis, first reversible motor means supported by said first member at a point removed from said axis, and adapted to move said first member with respect to said supporting means, a second member carried by said first member for rotation about a second axis substantially at right angles to said vertical axis, second reversible motor means carried on said first member at a point substantially diametrically opposed to said first motor means for angularly adjusting said second member with respect to said first member, a third member pivoted in said second member on athird axis substantially at right angles to both said vertical and second axes, third reversible motor means carried on said second member for varying the angular relation between said third and said second members, and gravity influenced motor control means in control of said second and third motor means for operating said second and third motor means on inclination of said normally vertical axis to maintain said third member in a fixed relation with respect .to horizontal.

2. In a leveling device, in combination, a support subject to inclination from a normal position, a member pivoted in said support on a normally horizontal axis, reversible motor means for positioning said member with respect to said support about said axis, first gravity influenced motor control means, said first control means being adapted to operate said motor means when said member is tilted a predetermined relatively small angle from a normal position, and second gravity influenced motor control means, said second control means being adapted to prevent operation of said motor means by said first control means when said support s tilted a predetermined relatively large angle from said normal position.

3. In a leveling device, in combination, a support subject to inclinations from a normal position, a member pivoted in said support for rotation about a normally horizontal axis, reversible motor means for positioning said member with respect to said support about said axis, first gravity influenced motor control-means adapted to cause operation of said motor means at a predetermined rate when said member is tilted a predetermined angle from a normal position, and

second gravity influenced motor control means auapted to cause operation of said motor means at a predetermined lower rate when said member is tilted a predetermined relatively smaller angle from said normal position.

4. In a leveling device, in combination, a support subject to inclinations from a normally horizontal position, a first member carried by said support and rotatable about a normally vertical axis, first reversible motor means carried by said first member at a point spaced from said axis and adapted to move said first member with respect to said support, a second member carried by said first member and rotatable about a second normally horizontal axis, second reversible motor means for moving said second member with respect to said first member, said second reversible motor means being substantially equal in weight to said first motor means and carried on said first member at a point spaced from said vertical l0 axis and substantially diametrically opposed to said first motor means.

SIEGFRIED G. ISSERSTEDT.

REFERENCES orrnn The following references are of record in the file of this patent:

NITED STATES PATENTS 

